Electric blankets, heating pads, hot water bottles and ice bags are well known hot/cold localized therapy devices. The electric blankets and heating pads generally have electrical resistance elements incorporated in soft plastic or natural fiber material. Temperature select control switches are provided for controlling the amounts of electrical power applied to the elements. The switch selects power ranges and therefore temperature ranges of the blankets or pads.
Similarly hot/cold therapy devices are used in hospitals; however, these devices are more sophisticated and costly. In these medically approved device,s a hot/cold fluid is circulated through a flexible conduit in the pad to provide a preselected temperature output. The fluid temperature is maintained by three interdependent systems: a refrigeration/heating system, a temperature control system, and a fluid circulating system. The refrigeration/heating system has included a compressor, refrigerant condenser, and evaporating coils for cooling the fluid. Again, heater elements are used where necessary for producing a hot fluid for circulation through the pad's flexible conduits.
More recently, a thermoelectric heat pump has been disclosed as a replacement for the refrigeration/heating system. The temperature control fluid circulating system utilizing the thermoelectric heat pump as the refrigeration/heating system includes a fluid tank having associated therewith at least one thermoelectric heat pump and a temperature sensor. A temperature controller is connected to the temperature sensor and to a power supply. The power supply is connected to the thermoelectric heat pump(s) and is responsive to the temperature control means for supplying power with the appropriate polarity to the thermoelectric heat pump to reach and maintain a selected fluid temperature.
The fluid circulating system includes a pump to force the fluid from the tank through a flexible connecting pipe for circulation through the flexible conduit of the pad and return to the tank through a flexible return pipe.
It is recognized that problems attend the use of a fluid circulation system. One problem is the increased mass which has to be cooled. The mass includes the fluid holding tank, flexible connecting pipes, pad flexible tube, and pad. Thus, to heat the pad to a preselected temperature requires a larger thermoelectric heat pump and more power and time than would be required if only the pad were to be heated.
Another problem is water condensation. Water condensing on the flexible tube of the pad wets the pad; thus, a water proofed pad is required. Water condensing on the flexible interconnecting pipes can drip on the floor creating safety hazards to the patient and to those attending to the needs of a patient. Finally water condensing on the tank can drip into the tank housing to generate rust and electrical shorting problems.
A disadvantage of the known refrigerator/heating system is the bulk of the system. The device is a portable device for movement from one hospital bed side to another, and once positioned occupies substantial bed side space, often in space competition with other required bed side devices.
Another disadvantage of the refrigerator/heating system is the attention required to maintain its proper operation. For example, the fluid tank must be filled and the fluid level maintained for proper operation. Further, the unit must be leveled after each moving for proper operation. Such units generally shut down automatically when tilted more than about eleven degrees. Failure to provide the required attention can result in equipment damage, operation failure, and the creation of safety hazards.